1. Field of Invention
This invention relates to fabric decoration, specifically screen printing onto fabric or clothing for novelty and decorative purposes.
2. Discussion of Prior Art
Thermochromic pigments were invented in 1970 by Dr Suzuki of Kirokusozai Sogo Kenkyusho Co. Thermochromic pigments have been commercially available in the United States for fabric decoration since the early 1990's. The commercially available thermochromic inks for fabric decoration have not become main-stream because they are expensive, they lack opacity and there is very little information readily available regarding their use.
U.S. Pat. No. 5,490,956 to Kito (1996) suggests concealing an object within a three dimensional plastic object composed of a clear plastic resin and thermochromic pigments. This process would work for a variety of decorative three dimensional objects such as a paper weight, but this process would not work well for clothing, because the heavy weight of the plastic needed to conceal an image on an article of clothing would result in the fabric sagging and constant stress on the fabric where the plastic was located, resulting in a deformed article of clothing and an uncomfortable fit for the person wearing the garment. Additionally, there could be laundering problems and manufacturing limitations. To yield acceptable results on clothing, a masking effect with a thin ink deposit is needed.
U.S. Pat. No. 6,604,854 to Limburg (2003) discloses a means for creating thermometers on plastic substrate films, decals and refrigerator magnets with sensors that appear and disappear from respective concealing features according to temperature. The first step in the process is to choose a standard ink that is appropriate for the intended plastic substrate. The standard ink is used later to print a hidden text message. Next, a thermochromic disappearing ink suitable for the intended plastic substrate is mixed in its non-activated/cold state so that it very closely or exactly matches the color of the standard non-disappearing ink previously chosen for the hidden text message. The hidden text message such as “Too Hot” is printed on the plastic substrate with the standard non-disappearing ink. The thermochromic disappearing ink is then printed around the hidden message. Because both inks match in color, it appears as though the two images printed are one continuous solid object. This camouflages the hidden text message. The described process would work well for use as a plastic sheet thermometer but if used for clothing decoration would suffer from a number of limitations and disadvantages:                (a) The inks described are intended for use on plastic film not fabric.        (b) The field of the invention is for temperature sensing devices (thermometers) that exhibit an interesting or graphic means to reveal or inform an individual of a temperature or temperature range with messages such as, “Too Hot”, “Warm”, and “Just Right”. My invention is not designed or intended to educate or inform temperature information, but rather to create interactive novelty clothing decorations that perform dramatic reversible metamorphic changes throughout the day for the person wearing the article of clothing.        (c) A minor change in temperature will alter the color of the thermochromic ink, resulting in two ink colors that would no longer match, thus revealing the image that you are trying to conceal too quickly. For novelty clothing, best results are achieved when a combination of concealment is used involving a thermochromic ink with a similar color value to the hidden image ink, which is screen printed around the hidden image followed by screen printing detailed line work composed of a dark thermochromic disappearing ink on top. “Color value” is defined as the relative lightness or darkness of a color. An exact color match or very similar color match is not needed with my invention if detailed line work consisting of a dark colored thermochromic ink is also printed over the image to be concealed.        (d) The process as described can only be printed on light colored or clear substrates. Thermochromic pigments are transparent in nature, and are virtually invisible when printed on dark substrates.        (e) Thermochromic pigments tend to degrade over time with prolonged exposure to Ultra-Violet (UV) light which results in an ink that does not return to the colorized state when cooled and eventually remains transparent at all times, regardless of temperature. Therefore, the applications described by U.S. Pat. No. 6,604,854 would result in short life expectancy of the temperature sensing devices when used outdoors, rendering them nonfunctional for the intended purpose. When screen printing for novelty purposes on clothing, should the thermochromic pigments fail to operate as designed, which would result in the thermochromic ink remaining invisible despite environmental temperature, the garment would still contain the interesting hidden image and could still be worn, which is clothing's primary function.        
3. Objects and Advantages
Accordingly, several objects and advantages of my invention are:                (a) To provide a novelty garment that interacts with an individual wearing the garment;        (b) To provide a novelty garment that performs dramatic transformations depending on the environmental temperature;        (c) To provide a means to incorporate a hidden graphic or message into a variety of screen printed fabric designs, which become revealed when a predetermined temperature is reached;        (d) To provide textile screen printers a thermochromic disappearing ink that is easy to work with and yields a very dark color value on light colored fabrics;        (e) To provide a means to produce decorations with hidden messages or hidden graphics or that perform transformations on dark colored fabric;        (f) To provide a means to decorate clothing with thermochromic ink, in which an appearance of a printed decoration changes and in which the appearance change is reversible depending on environmental temperature;        (g) To provide an article of novelty clothing that will maintain an appealing decoration and that will remain wearable in the event that the thermochromic pigmentation used to decorate the article of novelty clothing should fail to operate as intended due to prolonged exposure to UV light;        
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description